A stereoscopic image means a three-dimensional (3D) image which provides information regarding a depth and the shape of a space, as well as information regarding an image. A stereo image provides different viewpoint images to left and right eyes. In contrast, the stereoscopic image provides an image viewed in a different direction whenever an observer changes a viewpoint. Thus, images captured from a plurality of viewpoints are needed to generate a stereoscopic image.
The amount of data of images captured from various viewpoints to generate a stereoscopic image is large. Thus, if a network infrastructure, a ground wave bandwidth, etc. are taken into account for the stereoscopic image, the stereoscopic image is almost impossible to achieve although the images are compressed using an encoding apparatus optimized to single-view video coding such as MPEG-2, H.264/AVC, HEVC, etc.
Thus, a multi-view (multi-layer) video encoding apparatus optimized to generate a stereoscopic image is needed. In particular, technology of efficiently reducing redundancy between time and viewpoints is needed.
For example, according to multi-view video codec, an image captured from a basic viewpoint may be compressed through single-view video compression, and encoded by referring to the basic viewpoint when the image is expanded, thereby improving a compression ratio. Furthermore, auxiliary data such as a depth image may be additionally encoded to generate images from more viewpoints than viewpoints input from an image decoding side. Here, the depth image is used to synthesize images from intermediate viewpoints rather than being used to be directly viewed to a user. When the depth image deteriorates, the quality of a synthetic image is low. Thus, in multi-view video codec, not only multi-view video but also a depth image should be efficiently compressed.